Pre-fragmented shaped charge

ABSTRACT

The present invention provides an apparatus and method for controlling the debris generated by shaped charges during perforating. The controlled debris perforating system comprises a pre-fragmented shaped charge having a charge case and an explosive material.

FIELD OF THE INVENTION

[0001] The subject matter of the present invention relates to apre-fragmented shaped charge for use in perforating operations. Morespecifically, the subject matter of the present invention relates tocontrolling the debris generated by the shaped charges duringperforating.

BACKGROUND OF THE INVENTION

[0002] In drilling operations, the drilled hole is often lined with acasing to prevent the earth from filling the hole. In order for thesurrounding fluid to enter the drilled hole, the well casing must beperforated. Such operation is typically performed by a perforating gunloaded with one or more shaped charges.

[0003] Conventional shaped charges produce significant debris upondetonation. If small enough, the generated debris can exit the guncarrier and enter the well fluid and become entrained in the well fluid.The exit of the debris can occur both during detonation and during theretrieval process of the carrier to the surface. As the debris iscarried by the well fluid, it can complicate down stream processing ofthe well fluids by clogging filters and jamming pumps, for example.

[0004] There exists, therefore, a need for controlling the size ofdebris generated during perforating operations.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005]FIG. 1 is a cross-sectional view of a typical shaped charge,loading tube, and hollow carrier.

[0006]FIG. 2 is a perspective view of a typical shaped charge andloading tube.

[0007]FIG. 3 is a perspective view of a loading tube being inserted intoa hollow carrier.

[0008]FIG. 4 illustrates an embodiment of the pre-fragmented shapedcharge.

[0009]FIG. 5 provides a top view of an embodiment of the pre-fragmentedcharge case having 6 slots.

[0010]FIG. 6 provides a top view of an embodiment of the pre-fragmentedcharge case having 2 slots.

[0011]FIG. 7 provides a top view of an embodiment of the pre-fragmentedcharge case having 4 slots.

[0012]FIG. 8 illustrates an embodiment of the pre-fragmented chargecasing having V-notch slots.

[0013]FIG. 9 illustrates an embodiment of the pre-fragmented chargecasing having U-notch slots.

[0014]FIG. 10 illustrates an embodiment of the pre-fragmented chargecase having internal slots.

[0015]FIG. 11 illustrates an embodiment of the pre-fragmented chargecase having circumferential slots.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0016]FIG. 1 provides an illustration of a typical shaped charge,indicated generally as 1, used for perforating a well casing. Typicalshaped charges for use in perforating guns are discussed in U.S. Pat.No. 4,724,767 to Astatine issued Feb. 16, 1988; U.S. Pat. No. 5,413,048to Warner et al. issued May 9, 1995; U.S. Pat. No. 4,669,384 to Chawlaet al. issued Jun. 2, 1987; and again in U.S. Pat. No. 5,597,974 toVoreck, Jr. et al. issued Jan. 28, 1997. Each of the above mentioneddisclosures are incorporated by reference into this specification.

[0017] A typical shaped charge 1 includes a case 10, a main body ofexplosive material 12, which in the past has been, for example, RDX,HMX, PYX, or HNS packed against the inner wall of the case 10, a primer13 disposed adjacent the main body of explosive 12 that is adapted todetonate the main body of explosive 12 when the primer 13 is detonated,and a liner 14 lining the primer 13 and the main body of explosivematerial 12. The liner 14 acts to maintain the shape of the explosive toassure proper propagation of the detonation. A detonating cord 20contacts the case 10 of the shaped charge 1 at a point nearest the apexof the liner 14 of the charge. When a detonation wave propagates withinthe detonating cord 20, the detonation wave will detonate the primer 13.When the primer 13 is detonated, the detonation of the primer 13 willfurther detonate the main body of explosive 12 of the charge 1. Inresponse to the detonation of the main body of explosive 12, the liner14 will form a jet that will propagate along a longitudinal axis of theshaped charge 1. The jet will perforate a formation penetrated by thewellbore.

[0018] One or more shaped charges 1 are housed within a loading tube 22for transport. The loading tube 22 can house the shaped charges 1 atdesired orientations, or in a linear fashion. A jacket 24 is used toboth secure the shaped charges 1 to the loading tube 22 and to maintainthe orientation of the shaped charges 1. Once the loading tube 22 isready for delivery downhole, a hollow carrier 30 is used to carry theloading tube 22 and housed shaped charges 1.

[0019] In one conventional use shown in FIGS. 2 and 3, the shapedcharges 1 and jackets 24 are inserted into the loading tube 22 until thejackets 24 shoulder against the loading tube shoulders 23. Once all ofthe shaped charges 1 are secured, the loading tube 22 is inserted intothe interior of the hollow carrier 30. The hollow carrier 30 thentransports the shaped charges 1 downhole to the desired depth ofperforation.

[0020] It should be noted that the above description of the conventionshaped charges 1 is intended for illustration only and not intended tolimit the scope of the present invention. The present invention isequally applicable for use in alternate shaped charges and carriers. Forexample, the present invention can be used with equal applicability withjacket-less shaped charges.

[0021]FIG. 4 illustrates one embodiment of the pre-fragmented shapedcharge, indicated generally as 40, of the present invention. Slots, orgrooves, 42 are cut into the charge case 44 to weaken the case 44according to a certain pattern or design. Upon detonation of thepre-fragmented shaped charge 40, the case material is subject toexplosion forces and will undergo stretching in its hoop direction.Because the slots 42 are cut in the axial direction orthogonal to thehoop stretching, the slots 42 define weakening lines along thestretching direction. As a result, the charge case 44 will fracturealong these lines of weakness. In this manner, the pre-fragmented shapedcharge 40 can be used to control the size and shape of the debrisgenerated by the charge case 44 during perforating operations. The slots42 in the pre-fragmented shaped charge 40 can also be used to channelthe explosion energy in certain directions. Such channeling of explosiveenergy improves the survivability of the gun carrier 30.

[0022] As shown in FIGS. 5-7, the pre-fragmented shaped charge 40 can bedesigned with any number of slots 42. As examples, FIG. 5 displays acharge case 44 having 6 slots 42, FIG. 6 displays a charge case 44having 2 slots 42, and FIG. 7 displays a charge case 44 having 4 slots42. It should be understood that any number of slots 42 can be cut intothe charge case 44 depending upon the application. Because the distancebetween the slots 42 controls the size of the generated debris, forapplications in which it is desired to make the debris larger than theexit hole in the hollow carrier 30 (shown in FIG. 3), the pre-fragmentedshaped charge 40 may have fewer slots 42. Conversely, when it is desiredto make the debris very small, such as when the shaped charge 40 is usedfor spiral or strip guns, the charge case 44 may have many slots 42.

[0023] In addition to variances in the number of slots 42, the slots 42cut into the charge case 44 can be of multiple shapes and sizes. FIGS. 8and 9 illustrate two example slot 42 designs. In FIG. 8, the slot 42 cutinto the wall of the case 44 is a V-notch groove, while in FIG. 9, theslot 42 cut into the wall of the case 44 is a U-notch groove. The shapeand depth of the slot 42 controls the timing of the breakup of thecharge case 44.

[0024] Another embodiment of the pre-fragmented shaped charge 40 isillustrated in FIG. 10. In this embodiment, the slots 42 are cut on theinternal surface of the charge case 40.

[0025] Yet another embodiment of the pre-fragmented shaped charge 40 isillustrated in FIG. 11. In this embodiment, the slots 42 are orientedcircumferentially around the charge case 40. The circumferential slots42 can be internal or external.

[0026] The invention being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the invention, and all suchare intended to be included within the scope of the followingnon-limiting claims.

What is claimed is:
 1. A controlled debris perforating system,comprising: a pre-fragmented shaped charge having a charge case and anexplosive material.
 2. The controlled debris perforating system of claim1, wherein the charge case defines at least one slot.
 3. The controlleddebris perforating system of claim 2, wherein the at least one slot isaxially oriented.
 4. The controlled debris perforating system of claim2, wherein the at least one slot is circumferentially oriented.
 5. Thecontrolled debris perforating system of claim 2, wherein the at leastone slot is a U-notched groove.
 6. The controlled debris perforatingsystem of claim 2, wherein the at least one slot is a V-notched groove.7. The controlled debris perforating system of claim 2, wherein the atleast one slot is an external slot.
 8. The controlled debris perforatingsystem of claim 2, wherein the at least one slot is an internal slot. 9.A method of controlling the debris during perforating, comprising:providing a pre-fragmented shaped charge having a charge case defining aplurality of grooves.
 10. The method of claim 9, wherein the pluralityof grooves are axially oriented.
 11. The method of claim 9, wherein theplurality of grooves are circumferentially oriented.
 12. A shaped chargemade by a process, comprising: inserting an explosive into a case;inserting a liner over the main body of explosive; and machining aplurality of slots in the case.
 13. The shaped charge made by theprocess of claim 12, wherein the plurality of slots are U-notchedgrooves.
 14. The shaped charge made by the process of claim 12, whereinthe plurality of slots are V-notched grooves.
 15. The shaped charge madeby the process of claim 12, wherein the plurality of slots are machinedexternally.
 16. The shaped charge made by the process of claim 12,wherein the plurality of slots are machined internally.
 17. A method ofusing one or more pre-fragmented shaped charges in a well, comprising:providing a perforating string having one or more pre-fragmented shapedcharges; and conveying the perforating string into the well.
 18. Themethod of claim 17, wherein the perforating string comprises a loadingtube and carrier.
 19. The method of claim 17, wherein the perforatingstring comprises a spiral gun.
 20. The method of claim 17, wherein theperforating string comprises a strip gun.